Anode and process of making same.



No. 762,227. PATENTBD JUNE 7, 1904.

H. BLAGKMAN.

ANODE AND PROCESS OF MAKING SAME. APPLICATION rmm APR. 24, 1903.

NO MODEL.

FIG. 7.

I I I l' lfl i i (/Z 3;

. 1%VENT-OR: WITNESSES:

By Altomeys, v

UNITED STATES Patented June 7, 190 1.

PATENT OFFICE.

ANODE AND PROCESS OF MAKING SAME.

SPECIFICATION forming part of Letters Patent No. 762,227, dated June 7,1904.

Original applioation filed December 8, 1296, Serial No. 614,894. Dividedand this application filed April 24, 1903. Serial No. 154,163. (Nomodel.)

To all w/tom it may concern;

Be it known that I, HENRY BLAOKMAN, a citizen of the United States,residing in the borough of Manhattan, city, county, and State of NewYork, have invented certain new and useful Improvements in Anodes andProcesses of Making the Same, of which the following is a specification.

This invention relates to anodes for use in electrolytic decompositions,of which the electrolysis of sodium chlorid isa type, and is a divisionof my application for patent, Serial No. 614,89 l, filed December 8,1896.

My invention provides an improvement in anodes the exposed surface ofwhich is of dense electroconductive iron oxid. In my Patent No. 568,231,dated September 22, 1896, I have claimed an anode for use inelectrolytic decomposition, consisting of an electroconductive oxid ofiron in a dense impermeable mass. Such electroconductive iron oxid maybe magnetite (Fe3O4) or other magnetic iron oxid. According to my saidpatent I contemplated forming the anode as a plate or slab by sawing orchipping from the native mineral, such as magnetite or ilmenite, or byfusing the mineral with the addition of a flux and casting the plates orby applying the magnetic oxid as a coating upon an iron plate.

According to my present invention I provide an anode the interior ofwhich is of iron or steel, while the exterior is of magnetic iron oxid,the iron and the oxid being integral with one another-that is, bothbeing parts of one simple piece of metal and not being separately formedand then united into a compound plateand the oxid being of sufficientthickness and density to wholly cover and protect the iron from theoxidizing action during electrolysis. according to my present invention,I take a plate of cast-iron preferably (or wrought-iron or steel may beused) and oxidize its surface by suitable treatment in such manner as toconvert it into magnetic or electroconductive oxid and continue thetreatment until the oxid thus produced is of such thickness and densityas will effectually cover, inclose, and

to corrosive action elsewhere.

To produce this anode protect the underlying iron. Thus the oxidexterior is integral with the iron interior' that is to say, the two areone bodythe fibrous or crystalline structure of the iron extendingthrough the coating of oxid uninterrupted or unchanged except to theextent that the chemical character of the iron is changed by thecombination with itof oxygen.

Another feature of my invention consists in the protection of theelectrodes from the active corroding influence which occurs at thesurface ofthe electrolyte. I have found that an anode of even puremagnetic iron oxid suffers from corrosion at the surface of theelectrolyte, although perfectly resistant The cathode also is corrodedin like manner. I have tried numerous protective coatings .for shieldingthe electrodes at this point, such as vulcanized rubber and otherinsulating compositions, but without effect. I have therefore devised ameans for successfully protecting this portion of the electrode, whichconsists in covering it with a band of insulating and imperviousmaterial, such as glass or a vitreous glaze, united, as by fusing, uponthe surface of the electrode, so as to effectually prevent all electricaction at or near the surface of the electrolyte.

Figure 1 of the accompanying drawings is an elevation of an anode madein accordance with this invention. Fig. 2 is a section of the same onthe line 2 2 of Fig. 1. Fig. 3 is a section of the same on the line :0a; of Fig. 1.

Referring to the embodiment of the inven tion illustrated, A designatesthe anode-plate, which is immersed to the level of the line a; a; in theelectrolyte. The anode may be of any suitable shape above said level formaking electrical connection with the conductor or bus-bar connectingthe several anodes together. I prefer to form it with arms or el bowsextending first upwardly and then horizontally, as shown, theouter endsof these arms being clamped to the bus-bars by means of any suitablescrew-clamp. The shape of the electrodes, however, is not essential tomy invention.

The anode-plate A is first formed by cast-.

ing or forging and is then treated for the proper oxidation of itssurface or of that portion of its surface which is exposed below thelevel of the electrolyte. This treatment consists, essentially, inexposing it to oxidizing agents under such conditions as to convert theexterior portion of the iron into magnetic iron oxid, either F6304 orother composition of magnetic or electroconductive oxid. The treatmentmust be continued until the oxid is formed of sufficient thickness anddensity to be impermeable to the chlorin or other oxidizing agentsliberated at the anode during electrolysis in order that the layer ofoxid'may protect the underlying iron from corrosion. Not even theminutest pin-hole must be left unprotected.

The oxidation of the iron may be efiected in various ways. One suitablemode is to place the anode-plates in a mull-1e or retort and heat them,by passing burning gas through it or by heat otherwise applied, to atemperature of from 1,000 to 1,200 Fahrenheit and then to pass throughthe heated chamber steam which has been superheated to approximately thesame temperature under or slightly above atmospheric pressure, thisprocess being continued for several hours, ordinarily eight or tenhours, or until the coating attains'a thickness of from one to threemillimeters. It is advantageous during the process to inject into theretort a small quantity of naphtha or other light hydrocarbon, whichsomewhat modifies the nature of the coating, converting it partiallyinto a compound of hydrogen, iron, and carbon or a double carbid ofhydrogen and iron. This coating, however, has apparently the sameproperties under electrolytic action as a coating of pure magnetic ironoxid, and hence comes equally within my invention. At the conclusion ofthe treatment the anodes should be left in the retort and free from exposure to air until partially cooled to avoid danger of the oxid orcarbid coating scaling off by unequal contraction.

I also contemplate the oxidation of the exterior of the anodes by firstcoating the iron plate with a thin film of some other metal, as tin orbronze, and then exposing the same to a current of oxidizing-gas whileheated 'to 1,000 Fahrenheit or upward, whereby the oxygen penetratesthrough the surface-coating, oxidizes the body of the iron, and formsmagnetic oxid, the thickness of the latter in creasing according to theperiod of exposure. The original film of coating metal disappears duringthe process. The first coating may be applied by electroplating or bydipping.

I also contemplate the oxidation of the anodes by other chemicaltreatment. For example, a bath may be prepared of fused niter containinga small percentage of peroxid of manganese, which in an ordinarymelting-pot is kept at a temperature of about 650%Fahrenheit. Into thisbath the anodes may be plunged and left for a greater or less time untilthe iron surfaces are oxidized to the required depth.

Other chemical means exist by which the iron surface can be convertedinto electroconductive and acid resisting oxids. such process comeswithin the intent of my invention. My experience thus far, however,leads me to prefer the process first described by reason of itscapability of producing an oxidized layer of any desired thickness. Thethickness of oxid required bymy invention is much greater than thatrequired merely to protect iron from rusting under exposure toatmospheric conditions. The exact thickness depends upon the characterof the iron and the smoothness and uniformity of its surface, since aperfectly smooth iron casting wholly free from blow-holes andsand-pitting requires but a comparatively thin layer of oxidation, whilea defective casting requires that the oxidation shall be carried to suchdepth as to protect the iron where it is liable to be exposed by reasonof the imperfections.

It will be understood that the anode may be of steel instead of iron,the word iron as used in this specification and claims being intended toinclude steel.

For protecting the electrodes from corrosion near the surface of theelectrolyte each is provided with a band or layer of glass or vitreousglaze, (denoted at E.) This band is formed around that portion of eachelectrode adjacent to the level of the electrolyte and should becontinued, preferably, somewhat aboveand below this level in order tofully protect the plate from corrosion. Fig. 3 shows the anode incross-section, with its iron interior and oxidized surface and the glassband 0 around it. This band of glass may be applied in any manner knownto glass-workers-as, for example, by heating the anode to approximatelythe softening-point of glass and applying a strip of plastic orsemimolten glass around itor a glaze may be prepared in the form of apowder with a cementitious vehicle by which it is united to the anode,after which the latter may be baked in order to vitrify and set theglaze, as is practiced in the- Any.

netic iron oxid covering and protecting the iron interior.

2. An electrolytic anode the interior of which is of iron and theexposed exterior of which is of impermeable magnetic iron oxid integralwith said iron, and of thickness and density suflicient to protect theiron from the action of oxidizing agents developed at the anode duringelectrolysis.

3. An electrolytic anode consisting of a plate of cast-iron the surfaceof which is oxidized to a magnetic oxid of suflicient thickness densityand impermeability to protect the iron.

4. The process of making an anode which consists in casting a plate ofiron and oxidiz ing the surface thereof to a magnetic oxid of suflicientthickness density and impermeability to protect theiron.

5. The described process of making an anode, consisting in forming aplate of iron, and exposing it at a high temperature to the action ofsuperheated steam, until its exterior is converted into magnetic ironoxid of thickness sufficient to protect the underlying iron fromoxidation during electrolysis.

6. An electrode for electrolytic apparatus, having a protecting layer ofglass or Vitreous glaze fused to it in a band around that portion of theelectrode Which is destined to be exposed at the surface of theelectrolyte.

7 An anode for electrolytic apparatus, the exposed exterior of which isof dense impermeable magnetic iron oxid, having a protecting layer ofglass or vitreous glaze fused to it in a band around that portion of theanode Which is destined to be exposed at the surface of the electrolyte.

In Witness whereof I have hereunto signed my name in the presence of twosubscribing Witnesses.

HENRY BLACKMAN. Witnesses:

FRED WHITE, THOMAS F. WALLACE.

